1. Field of the Invention
The present invention relates to a photoelectric conversion element, an image reading device, an image forming apparatus, and a photoelectric conversion method.
2. Description of the Related Art
As a complementary metal oxide semiconductor (CMOS) image sensor, one of a column type has been known that has a floating diffusion (FD) amplifier per pixel, and that has an analog digital convertor (ADC) per column so that one line is selected from a pixel array to be read out at the same time in a column direction for an output thereof, and that extracts an image signal as a digital signal.
Moreover, among CMOS line sensors, there is one in which a processing circuit for one column is configured with, for example, three pixels of R/G/B for pixels that R/G/B are aligned in a main scanning direction, and in which pixel signals that have been processed in multiple columns in parallel are serialized to be read. However, because image signal lines of several thousands of columns are connected to a data bus to read image signals, the wiring capacity is to be large and the drive capacity becomes low, resulting in a limit in speedup.
Furthermore, in Japanese Laid-open Patent Publication No. 2010-41460, a solid-state imaging apparatus is disclosed in which multiple pieces of pixel data that are divided into a predetermined number of division pixel-data groups are fetched in a predetermined number of data blocks, each of the predetermined number of data blocks includes a data line for reading a corresponding division pixel-data group, and an amplifier unit that amplifies a signal of the data line to output as a block data output with predetermined timing, the predetermined number of data blocks are connected such that a block data output of a preceding stage is given to a data line at a following stage as a block data input, and a block data output of a data block at a final stage is to be a final data output.
Because a line sensor generally has a chip structure long in one direction, a logic unit for post processing to be integrated is arranged at either one of two end portions, and according to a constraint in layout when mounting in an image reading device, a transmission distance of image data to a device at a subsequent stage is long. If the transmission distance of image data to a device at a subsequent stage is long, the quality of transmission waveforms can be deteriorated or a skew margin can be small, and therefore, thereby making it difficult to achieve speedup. Moreover, because a cable is laid for a long distance to transmit a high-speed signal to a subsequent stage, there has been a problem that an adverse effect is caused on electromagnetic interference (EMI).
Therefore, it is desirable to provide a photoelectric conversion element, an image reading device, an image forming apparatus, and photoelectric conversion method that enable to shorten a transmission distance of output image data without decreasing processing efficiency of read data at a subsequent stage even when there is a constraint in layout at the time of mounting.